Caterpillar Track Complexes in Template‐Directed Synthesis and Correlated Molecular Motion

Abstract

Small alterations to the structure of a star-shaped template totally change its mode of operation. The hexapyridyl template directs the conversion of a porphyrin dimer to the cyclic hexamer, but deleting one pyridine site changes the product to the cyclic decamer, while deleting two binding sites changes the product to the cyclic octamer. This surprising switch in selectivity is explained by the formation of 2:1 caterpillar track complexes, in which two template wheels bind inside the nanoring. Caterpillar track complexes can also be prepared by binding the hexapyridyl template inside the 8- and 10-porphyrin nanorings. NMR exchange spectroscopy (EXSY) experiments show that these complexes exhibit correlated motion, in which the conrotatory rotation of the two template wheels is coupled to rotation of the nanoring track. In the case of the 10-porphyrin system, the correlated motion can be locked by binding palladium(II) dichloride between the two templates.

Exploring template-bound dinuclear copper porphyrin nanorings by EPR spectroscopy

“…18,19 Since the precursor to c -P10 Cu2 is a linear pentamer containing one copper porphyrin as the central unit, the two copper porphyrin units in the ten-membered ring will necessarily be sitting opposite each other, separated by four zinc porphyrin units on either side. The positions of the copper centers in the free ring are therefore well defined.…”

Recent advances in the template-directed synthesis of porphyrin nanorings

“…It was found that the operation mode of the classical templating method could be totally changed only by small alterations to the structure of a star-shaped template. 31 As shown in their previous reports, the regular D 6h hexapyridyl template 11 directs the conversion of porphyrin dimer 10 to the cyclic hexamer 9 (Scheme 3). However, deleting one pyridine site of 11 changes the main product to the cyclic decamer 42, while deleting two adjacent pyridine binding sites changes the main product to the cyclic octamer Other templating methods have been developed for the synthesis of more complicated porphyrin nanorings.…”

Supramolekulare Chemie von gespannten Kohlenstoffnanoreifen

“…Darüber hinaus ermöglichte ein Ansatz mit Lochmaske den Austausch von Magnesiumzentren durch andere Metalle und ebnete damit einen neuen Weg zu heterometallischen Porphyrin‐Nanostrukturen . Nach Entfernung der Template boten Andersons Porphyrin‐Nanoringe im Allgemeinen eine interessante Plattform zur Untersuchung der Thermodynamik und Kinetik von multivalenter Gastbindung …”